9-Anilinoacridine derivatives have been extensively studied as potential antitumor agents, since they are capable of intercalating into double-stranded DNA and are inhibitors of topoisomerase II (Topo II). Many 9-anilinoacridine derivatives and their structure-activity relationships have been reported; see, for examples, Atwell et al., J. Med. Chem. 1972, 15:611; Cain et al., J. Med. Chem. 1974, 17:922; Cain et al., J. Med. Chem. 1975, 18:1110; and Rewcastle et al., J. Med. Chem. 1986, 29:472. Among these compounds, m-amsacrine 4'-(9-acridinylamino)methanesulfon-m-anisidine, m-AMSA! and its 5-methyl-4-methylcarboxamide derivative (known as CI-921) were of particular interest. Cain et al., Eur. J. Cancer 1974, 10:539 and Arlin Z., Cancer Treat. Rep. 1983, 967 reported the clinical use of m-AMSA for the treatment of acute leukemia. Baguley et al., Cancer Res. 1984, 44:3245 and Denny et al., J. Med. Chem. 1987, 30:658 described the phase II trials of CI-921 for treatment of leukemia and solid tumors. The antitumor activity of m-AMSA is attributed to Topo II-mediated cleavage of double-stranded DNA, by a mechanism which appears to be common to DNA-intercalating agents; see, for examples, Nelson et al., Proc. Natl. Acad. Sci. USA, 1984, 81:1364 and Pommier et al., Cancer Res. 1985, 41:3143.
Both m-AMSA and CI-921 possess a methanesulfonyl and a methoxyl function at C-1' and C-3' of the anilino ring and readily undergo reversible oxidation chemically or microsomally giving the quinonediimine (m-AQDI); see, for example, Shoemaker et al, Cancer Res. 1984, 44:1939 and Shoemaker et al., Drug Metab. Dispos. 1982, 10:35. When mouse and rat were treated with m-AMSA, the major biliary metabolites of this agent were the 5'- and 6'-glutathione (GSH) conjugates, with no C9-GSH conjugate being found; see for example, Shoemaker et al, Cancer Res. 1984, 44:1939, supra; Shoemaker et al., Drug Metab. Dispos. 1982, 10:35, supra; Robertson et al., Drug Metab. Drug Interact. 1988, 6:371; and Robertson et al., Xenobiotica 1992, 22:657. In the case of CI-921, in addition to the 5'- and 6'-GSH conjugates, two other metabolites, namely C9-GSH and the 4-hydroxymethyl derivatives of CI-921, were detected (Robertson et al., Xenobiotica 1992, 22:657, supra). More than 50% of the dose was excreted as the glutathione conjugate in the bile when the mouse was treated with these two drugs. The half-life of m-AMSA in the presence of fresh mouse blood at 37.degree. C. is ca. 30 min. See, for example, Shoemaker Drug Metab. Dispos. 1982, 10:35 supra and Robertson et al., Drug Metab., Drug Interact. 1988, 6:371, supra.
Chou et al., Am. Assoc. Cancer Res. 1994, 368 recently reported a series of 9-anilinoacridine analogues in which the 9-amino was substituted by an O or S atom or compounds lacking the substituent at the para position of the 9-amino function of acridine. These new series of compounds are incapable of forming diiminoquinone intermediate by oxidation and are, therefore, expected to have longer duration of drug action with higher chemotherapeutic effect. Among these compounds, 3-(acridin-9-yl)amino-5-hydroxymethylaniline (AHMA) was shown to have significant antitumor activity both in vitro and in vivo. The preliminary antitumor efficacy of AHMA and its derivatives indicated that 1) AHMA and its derivatives represent a novel type of antitumor agents which have a longer plasma half-life (1.5 h) than m-AMSA; and 2) AHMA has greater efficacy against murine leukemia and solid tumors (a mammary adenocarcinoma, B-16 melanoma and Lewis lung carcinoma) than m-AMSA and VP-16, and yet is less toxic toward the host.
Su et al., Journal of Medicinal Chemistry, 1995, 38:17 disclosed N-(tert-butoxycarbonyl)-3-(9-acridinylamino)-5-(hydroxymethyl)aniline as an intermediate for preparing 3-(9-acridinylamino)-5-aminobenzyl N-methylcarbamate. However, the pharmacological activity of the intermediate were not described therein.
We have surprisingly found that the N-alkoxycarbonyl derivatives of AHMA, i.e. the alkyl N-3-(acridin-9-yl)amino-5-hydroxy-methyl!phenylcarbamate derivatives, possess even better antitumor efficacy in vitro and in vivo than their precursor, AHMA (Tables 1 and 2, infra).